This invention relates to an exhaust brake control system and, more particularly, to an exhaust brake control system for an automotive vehicle equipped with an automatic transmission.
An exhaust brake control system installed in an automotive vehicle equipped with an automatic transmission is well-known in the art. For example, the specification of Japanese Patent Kokoku Publication No. 58-28414 describes an exhaust brake control system in which an exhaust brake is controlled by signals from an exhaust brake switch (hereafter referred to as an input switch) provided on the vehicle instrument panel or the like, a throttle switch actuated in dependence upon the amount by which the vehicle accelerator pedal is depressed, and a shift switch actuated by manual control of the automatic transmission.
The disclosed arrangement is particularly directed to freeing the driver from the troublesome task of operating the input switch when necessary by enabling the shift switch actuated by manual operation of the automatic transmission to be used an an exhaust brake starting switch. However, merely providing the shift switch as proposed by the cited invention is not enough to improve the performance of the exhaust brake. For example, when the arrangement is applied to an automatic transmission of the kind shown in FIG. 4, if the driver shifts to "2" to "L" manual select range when performing a downshift, the automatic transmission is in a so-called "neutral" state until any of prescribed servo piston cylinders is filled with the oil producing the servo hydraulic pressure that establishes the 2nd or 1st speed range, respectively, of the automatic transmission. When the abovementioned downshift to "2" or "L" manual select range is made, in the neutral state there is the possibility that the engine will stop running.